Loki from Marvel could be an interesting main character. He has his own charm and mischievous nature. If he somehow gets involved with the Harry Potter world, his wits and powers could attract characters from both universes, creating a harem around him.
Harry Potter himself could be the main character. His status as the Boy Who Lived gives him a certain allure. In a crossover, he could find himself in the Marvel universe and interact with various female characters there, like Black Widow or Scarlet Witch, forming a harem.
Black Widow could be one. She's attracted to his unique magic skills and his sense of justice. Another could be Peggy Carter. Her old - fashioned values might be charmed by Harry's chivalrous ways. And then there's Shuri. She'd be interested in Harry's magic as she is into new and different forms of technology and power.
A young half - blood wizard could be a great main character. They might have grown up in a muggle neighborhood but always felt a connection to the magical world. Once at Hogwarts, their ability to empathize with magical creatures makes them stand out, and gradually they attract a harem of creatures.
Peter Parker (Spider - Man) could also be a great main character for this kind of fanfiction. His youthful charm and heroic nature would appeal to characters in both universes. He could be on a school exchange program in Hogwarts (using some multiverse - like excuse) and during his stay, he gets involved with helping the wizards while also catching the eyes of Ginny Weasley, MJ, and Black Widow, creating an interesting harem situation.
Another possibility is Hermione Granger. She is intelligent, brave, and resourceful. In this type of fanfiction, she could gather a group of interesting characters around her. Maybe she could have relationships with characters like Tyrion Lannister for his wit and Ned Stark for his honor. This would create a very different dynamic compared to if a male character was the main one, and would explore different aspects of the harem concept in this crossover.
It could be a new student who has the blood of both a wizard and a demigod. This unique heritage gives them access to both worlds and also makes them extremely interesting to the other characters. For example, they might have the magical abilities of a wizard like being able to cast spells, and also the physical and combat abilities of a demigod. Characters like Hermione and Annabeth would be drawn to this new student's intelligence and resourcefulness, while others like Ginny and Piper might be attracted to their courage and unique powers, making them the center of a harem - like group.
In a 'Harry Potter in Marvel Harem Fanfiction', perhaps Voldemort also makes his way into the Marvel universe. Harry has to not only deal with the threats in this new world but also build his harem. He could use his knowledge of magic to train some of the Marvel characters. His relationship with the female characters in his harem could be based on mutual respect and admiration. For example, he might teach Spider - Man some spells in exchange for help in finding a way back home, and during this, he attracts characters like Storm and Jean Grey who are intrigued by his different kind of power.
It could be Harry Potter himself. Imagine Harry being sent to the Star Wars universe. His heroic nature and powerful magic would attract various characters. Maybe Rey from Star Wars would be interested in his magic and his ability to stand up against dark forces. And some female Hogwarts students might also be part of his 'harem' as they continue to support him in his new adventures.
Hermione could be a main character. Her intelligence and thirst for knowledge would make her really interested in the Jedi and their ways. Harry Potter himself could also be there, as his heroic nature might attract the attention of the other characters in the harem. And perhaps a Jedi like Rey could be brought into the mix, being a strong female character who could hold her own in both the wizarding world and among the Jedi.
Harry Potter would be the central character. In the MCU side, Captain America could play a major role. His old - fashioned values might clash or complement Harry's magical upbringing. For the harem, Gamora would be a great addition. She has her own strong - willed nature and combat skills. Another character could be Shuri. Her scientific genius could be fascinated by Harry's magic, and she could try to understand and even replicate it. These characters would create a diverse and interesting dynamic in the fanfiction.
Obviously, Harry Potter would be one of the main characters. From the Stargate side, Jack O'Neill could be an interesting addition. In the harem, Hermione could be there as she has always been close to Harry in the Potter universe. Also, a female Goa'uld could be part of the harem, bringing her own brand of power and mystery.